Apparatus for selective plating

ABSTRACT

A method of selective or &#39;&#39;&#39;&#39;spot&#39;&#39;&#39;&#39; plating, particularly electroplating, of articles including the steps of masking predetermined portions of the article to be plated so that those portions will not be contacted by the plating solution, establishing an electrical connection to conductive portions of the article and then contacting the unmasked portions of the article with plating solution, for sufficient length of time to plate those portions. The apparatus includes means for feeding the article into an apertured conveyor belt which forms the mask between the portions of the article to be plated and those portions which are not to be plated. The masked portion of the article is then contacted by a conductive liquid and the unmasked portion of the article contacted by the plating solution, through means of a reciprocating plating head which travels with the conveyor for a sufficient length of time to affect the plating of the unmasked portions of the article.

United States Patent [191 Schlotthauer [451 July 29, 1975 1 1 APPARATUSFOR SELECTIVE PLATING [75] Inventor: Roy Schlotthauer, Phoenix, Ariz.

[73] Assignee: Motorola, Inc., Chicago, Ill.

[22] Filed: Aug. 5, 1974 [21] Appl. No.: 495,005

Johnson et a1. 204/224 R Primary Examiner'l. M. Tufariello Atmrney.Agenl, 0r Firm-Vincent J. Rauner; Henry T. Olsen [57] ABSTRACT A methodof selective or spot plating, particularly electroplating, of articlesincluding the steps of masking predetermined portions of the article tobe plated so that those portions will not be contacted by the platingsolution, establishing an electrical connection to conductive portionsof the article and then contacting the unmasked portions of the articlewith plating solution, for sufficient length of time to plate thoseportions. The apparatus includes means for feeding the article into anapertured conveyor belt which forms the mask between the portions of thearticle to be plated and those portions which are not to be plated. Themasked portion of the article is then contacted by a conductive liquidand the unmasked portion of the article contacted by the platingsolution, through means of a reciprocating plating head which travelswith the conveyor for a sufficient length of time to affect the platingof the unmasked portions of the article.

3 Claims, 5 Drawing Figures SHEET PATENTEI] JUL 2 9 I975 mmdE+oooooooooooooon: D TOOOOOOW APPARATUS FOR SELECTIVE PLATING BACKGROUNDOF THE INVENTION This invention is related to a method and apparatus forelectroplating articles, and more particularly to a method and apparatusfor plating semiconductor package headers.

Previous attempts to selectively plate transistor headers have not beensuccessful, as they have been too cumbersome to be adapted for massproduction purposes. By selective plating is meant, as related totransistor headers, the plating of only the base and inner leads of theheader and not the outer portion of the base and the outer leads. Toaccomplish this previously required complicated or manual procedureswhich were not adaptable to mass production. As a result, mosttransistor headers have been bulk plated, which is somewhat wasteful ofthe plating material.

SUMMARY OF THE INVENTION It is therefore an object of the invention toprovide a method of selectively plating articles.

A further object of the invention is to selectively plate transistorheaders.

A still further object of the invention is to provide a method andapparatus for selectively plating transistor headers which is suitablefor mass production.

In accordance with these objects, there is provided a method andapparatus for automatically masking the transistor headers, contactingportions of the transistor header to render those portions to be platedelectrically conductive, and then contacting only those portions of thearticle to be plated with the plating solution.

THE DRAWINGS Further objects and advantages of the invention will beunderstood from the following complete description and from the drawingswherein:

FIG. 1 is a perspective view somewhat schematically of an assembly linefor selectively plating transistor headers in accordance with apreferred embodiment of the invention.

FIGS. 2a and 2b are a top and side view further illustratin g theoperation of the apparatus in contacting the transistor headers.

FIG. 3 is a cross-section of a detail illustrating the operation of theapparatus.

FIG. 4 is an exploded view depicting the relationship of the conveyorbelt to the electrical contact mechamsm.

COMPLETE DESCRIPTION The method of the present invention will be betterunderstood by reference to the preferred embodiment of the apparatuswhich, as shown in FIG. 1, includes two parallel conveyor lines 11 and12. Each conveyor line is fed with articles to be selectively platedfrom vibratory feeder bowls l3 and 14. The conveyor belts -l1 and 12then feed the articles to reciprocating plating heads 15 and 16 and thento an unload station whereat the articles can be removed and inspected.All of the foregoing can be mounted on and within a cabinet 17. Sincethe plating solution may give off undesirable odors and gasses, hoodsections 18 and 19 may be provided over the actual plating area.

After the articles are fed onto the conveyor belt 11 from the feeder,the track of the conveyor slopes downwardly at 30 (FIG. 2) toward theinterior of the cabinet support 17 within which a plating solutionrecovery tank 21 and a pump for circulating the plating solution throughthe plating heads is located. At the lower part 22 of the conveyortrack, the plating head 15 moves down into contact with the articles onthe conveyor, then travels with the conveyor while the plating takesplace, then moves upwardly and returns to plate the next group ofarticles, as indicated by the dashed travel line 23. The relationship ofthe conveyor belt 11 with relation to the plating head and itsconfiguration, is illustrated in detail in FIGS. 3 and 4 wherein it willbe noted that the conveyor belt has a plurality of centrally spacedmasking apertures 31 centrally located therein and the belt hasdownwardly curved wings on either side 32. The underside of the conveyorbelt is provided with alignment guides 33. The alignment guides 33cooperate with suitable members of the conveyor pulleys and thecontactor tank 34 to maintain the conveyor belt 11 in its proper track.The plating head 15 includes a lower plating chamber 35 defined bydownwardly extending side walls 36, 37 in an upper reservoir chamber 38.Suitable valving means may be provided in the inlet 39 between thereservoir chamber and the plating chamber. Since the plating solutionflows continuously from the plating reservoir 38 to the plating chamber35 during the plating operation, overflow ports 39 provide an outlet forthe plating solution, which then drains out over the wings 32 of theconveyor belt 11 for return to the plating tank 21.

Insofar as previously described, the apparatus would be suitable forelectroless plating, but is more particularly suitable for electrolyticplating and, therefore, the contactor tank 34 contains a conductiveliquid 40, such as mercury, which will establish one electricalconnection to the article to be plated. The other electrical connectionto the plating solution is provided by a conductive contact 41 liningthe inlet port 39. Thus, for example, the contact 41 provides the anodeto the plating solution and the conductive liquid 40 provides thecathodic contact, completing the electrolytic plating circurt.

The apparatus is particularly adapted for selectively plating transistorheaders. As shown in FIG. 3 the header includes a base 50 and aplurality of leads 57, one of which is electrically connected to thebase and the others being insulated therefrom. The level of conductiveliquid 40 is such that the leads 57 are in electrical contact therewith.

While the invention has been disclosed by way of certain preferredembodiments, it will be appreciated that suitable modifications may bemade therein without departing from the spirit and scope of theinvention.

What is claimed is:

1. Apparatus for selective plating of articles having conductiveportions to be plated and conductive portions extending therefrom not tobe plated comprising a conveyor belt having apertures; means for feedingthe articles into the apertures with the portions not to be platedextending therethrough, thereby masking those portions of the articlefrom contact by the plating solution; means for moving the conveyor beltso that conductive liquid means establish an electrical connection tothose portions of the article extending through the belt; and, platingheader means for contacting the unmasked portions of the article withplating solution for a sufficient length of time to plate thoseportions.

4 and through said plating head and whereby said conveyor belt isconfigured to drain the excess plating solution away from contact withthe conductive liquid means.

1. APPARATUS FOR SELECTIVE PLATING OFARTICLES HAVING CONDUCTIVE PORTIONSTO BE PLATED AND CONDUCTIVE PORTIONS EXTENDING THEREFROM NOT TO BEPLATED COMPRISING A CONVEYOR BELT HAVING APERTURES, MEANS FOR FEEDINGTHE ARTICLES INTO THE APERTURES WITH THE PORTIONS NOT TO BE PLATEDEXTENDING THERETHROUGH, THEREBY MASKING THOSE PORTIONS OF THE ARTICLEFROM CONTACT BY THE PLATING SOLUTION, MEANS FOR MOVING THE CONVEYOR BELTSO THAT CONDUCTIVE LIQUID MEANS ESTABLISH AN ELECTRICAL CONNECTION TOTHOSE PORTIONS OF THE ARTCLE EXTENDING THROUGH THE BELT, AND, PLATINGHEADER MEANS FOR CONTACTING THE UNMASKED PORTIONS OF THE ARTICLE WITHPLATING SOLUTION FOR A SUFFICIENT LENGT OF TIME TO PLATE THOSE PORTIONS.2. Apparatus as recited in claim 1 and further including means forreciprocating the plating head means in a rectilinear travel patternwhereby the plating header means travels with the conveyor belt for saidtime.
 3. Apparatus as recited in claim 1 and further including means foreffecting the flow of plating solution to and through said plating headand whereby said conveyor belt is configured to drain the excess platingsolution away from contact with the conductive liquid means.